The present application relates to a semiconductor design technology, and more particularly, to technology for configuring a delay circuit.
FIG. 1 is a block diagram of a conventional delay circuit. Referring to FIG. 1, the conventional delay circuit includes a plurality of unit delays 10 to 17 connected in series. A plurality of selection signals SEL<0:7> are allocated to the plurality of unit delays 10 to 17, respectively. The unit delays 10 to 17 selectively transfer their input signals to next unit delays in response to the selection signals SEL<0:7>.
The delay circuit controls eight unit delays 10 to 17 in response to eight selection signals SEL<0:7>.
When the first selection signal SEL<0> is activated and the other selection signals SEL<7:1> are deactivated, the input signal IN is delayed by the first unit delay 10.
When the first and second selection signals SEL<1:0> are activated and the other selections signals SEL<7:2> are deactivated, the input signal IN is delayed by the second unit delay 11 and then delayed by the first unit delay 10.
When the first to third selection signals SEL<2:0> are activated and the other selection signals SEL<7:3> are deactivated, the input signal IN is delayed by the third unit delay 12, the second unit delay 11, and the first unit delay in sequence.
That is, the delay circuit of FIG. 1 determines the delay value of the input signal IN in response to the number of the successively activated selection signals, starting from the first selection signal SEL<0>.
The conventional delay circuit can generate eight delayed signals having different delay values by using the eight selection signals and the eight unit delays. That is, N delayed signals can be generated by using N-bit selection signals and N unit delays, where N is a natural number. However, the conventional delay circuit needs a lot of selection signals and a lot of unit delays in order to generate delayed signals having different delay values. Thus, the overlapping of the circuits increases and thus a circuit area increases.